Serodiagnosis of Chlamydia trachomatis infections by the micro-immunofluorescence test

Kim, Sun E; Choi, Tae Yeal; Kim, Sinkyung; Kim, Kyung Suk

Abstract

BACKGROUND
Chlamydia trachomatis (C. trachomatis) is an obligatory intracellular parasite which causes trachoma, inclusion conjunctivitis, pneumonia in infants, nongonococcal urethritis, epididymitis, cervicitis, and salpingitis. Salpingitis frequently produces tubal damage and infertility. The micro-immunofluorecence (MIF) test is the standard method for chlamydial serology and is highly sensitive and specific. This study aimed to evaluate the prevalence of C. trachomatis antibodies in healthy individuals and patients with various diseases as well as the clinical value of chlamydial serology by MIF testing.
METHODS
A total of 692 serum samples were collected. Of these, 388 samples were obtained from healthy individuals (male 209, female 179). Cord blood samples were collected from 38 healthy babies. Serum samples of 53 female patients with infertility due to PID (group 1), 107 patients with respiratory diseases (group 2; pneumonia, bronchitis, etc.), and 106 patients with cardiovascular diseases (group 3; angina pectoris, acute myocardial infarction, etc.) who were admitted to Hanyang University Hospital from March 1995 to June 1998 were enrolled in this study. Serological diagnosis of a previous infection was made when IgG antibody titers to C. trachomatis were 1:32 or higher. A single titer of antibody of > or =1:512 for IgG or > or =1:16 for IgM was considered to indicate a recent infection.
RESULTS
The IgG antibody detection rate in healthy individuals was 27%, broken down by age as follows: < or =10 year old, 36%; 11 to 20 years old, 17%; 21 to 30 years old, 28%; 31 to 40 years old, 36%; 41 to 50 years old, 25%; 51 to 60 years old, 26%; > or =61 years old, 24%. For cord blood, the antibody was detected in 29% of the samples. There were 1 case (0.3%) of recent infection with C. trachomatis by IgG, and 6 cases (1.5%) for IgM. The incidence of IgG antibodies to C. trachomatis in the disease group was 70%, 28%, and 19% for group 1, group 2, and group 3, respectively. There were 3 cases of recent infection detected by IgG and 4 cases by IgM in group 1. Recent infection with C. trachomatis was detected by IgG in 1 case of group 2 and by IgM in another case of group 3.
CONCLUSIONS
In healthy individuals, the prevalence of antibodies to C. trachomatis was highest in those between the ages of 21-40 years. Patients with infertility due to PID showed a significantly higher positive rate (P=0.000 by Chi-square test) and more cases of recent infection to C. trachomatis than others. The results suggest that a positive chlamydial serology indicates a higher risk for infertility due to PID.